The present invention relates to rotary machines and, more particularly to rotary machines of the type used as pumps or compressors. In many such machines, a stator housing defining a stator chamber is provided in which is rotatably mounted a rotor. The rotor carries radially movable vanes which co-operate with the inner surface of the stator chamber to form discrete chambers which vary volumetricaly as the rotor, carrying the vanes, rotates within the stator. In machines of this type, the rotor will typically be mounted for rotation about an axis which is off-center with respect to the stator chamber in which it rotates. The rotor vanes are mounted on the rotor such that they may move radially with respect to the rotor to remain in contact with the surface of the stator chamber. Various arrangements have been used in the past in order to position the vanes properly with respect to the rotor such that the vanes will form the desired discrete chambers within the stator.
U.S. Pat. No. 3,955,540, issued May 11, 1976, to Blanchard discloses a rotary, internal combustion engine in which a rotor carrying vanes is rotatably mounted in a housing. The vanes are spring loaded to maintain their outer tips in sliding engagement with the inner surface of the housing and rollers on their inner ends in engagement with a vane race. With this construction, the vanes are pressed into engagement with the inside wall of the stator housing and necessarily there are substantial frictional energy losses as well as appreciable wear, not only of the vane tips, but also of the wall of the stator housing.
U.S. Pat. No. 3,988,083, issued Oct. 26, 1976, to Shimizu et al discloses a pump in which frictional engagement between the vane tips and the inside wall of the casing is eliminated by providing annular, outside races which are engaged by followers associated with the vanes. This arrangement limits the outward movement of the vanes into contact with the inner wall of the casing. Cylindrical springs inwardly of the followers urge the followers into contact with the races. As the pressure in each of the chambers defined by the vanes increases, the vanes may be lifted away from the inner surface of the casing, resulting in substantial leakage around the vanes and operating inefficiency of the pump.
U.S. Pat. No. 870,290, issued Nov. 5, 1907, to Henkel and U.S. Pat. No. 118,993, issued Sept. 12, 1871, to Wentworth, both disclose rotary machines having bearing followers which track through annular grooves in the interior of the stator housing. Since the interior and exterior surfaces of the annular grooves are fixed, however, it will be appreciated that substantial sliding must occur between the bearing followers and the groove surfaces during rotation of the rotors.
U.S. Pat. No. 2,672,282, issued Mar. 16, 1954, to Novas, discloses a rotary device in which the rotor vanes are positioned by blocks moving in an annular channel in the stator housing. A ball bearing race in the annular channel facilitates movement of the blocks. This configuration may be subject to substantial vibration as extensions of the vanes strike the blocks during rotation.
In U.S. Pat. No. 4,133,618, issued Jan. 9, 1979 to Ronald E. Smolinski, rotary machine is disclosed in which radial movement of the vanes is accomplished by means of cam followers which are attached to the vanes and which ride on stationary cam surfaces. Tension springs draw the vanes radially inward of the rotor so that the cam followers are held in contact with the cam surfaces. Such an arrangement may require springs which are manufactured to precise tolerances, however.
Accordingly, it is seen that there is a need for an improved rotary machine in which positive positioning of the rotor vanes is accomplished with minimal friction by the vane positioning structure.